The invention relates to sealing assemblies and, more particularly, to sealing assemblies for internally sealing a joint between hollow members.
In a number of installations, particularly underground installations, joints between pipes or other hollow members are vulnerable to an undesired inflow of liquids from an external source. One such installation is the manholes for municipal sanitary sewers. The seal at the so-called corbel joint between the flange of the cast iron manhole frame and the masonry chimney portion or casing of the manhole is frequently broken from traffic loading and/or subsurface heaving caused by drastic ambient temperature changes during the summer and winter months. When this occurs, water flowing through the corbel joint and into the sanitary sewer can contribute to the possibility of overflow conditions at the waste treatment plant(s) during or shortly after rain storms.
One approach for alleviating this problem involves the use of a sealing assembly including a flexible tubular sleeve or boot which fits inside the manhole and spans the corbel joint and a pair of expansion units for compressing the sleeve radially outwardly into sealing engagement with the interior walls of manhole frame and the manhole casing at the opposite sides of the corbel joint.
For example, the Modi U.S. Pat. No. 4,305,679 discloses such a sealing assembly including expansion units having an outer rim which engages the inside of the sleeve, a concentric hub, and a plurality of threaded spokes. Nuts on the spokes are turned to radially expand the ring. The expansion units must be removed each time a workman needs to enter the sewer through the manhole. Also, radial compression on different segments of the outer rim can vary depending on how much the nut on the corresponding spoke is tightened. Consequently, it is difficult to insure that a uniform seal is provided around the entire circumference of the sleeve.
Enclosed is a Cretex brochure illustrating and describing another prior sealing assembly including a rubber sleeve having a corrugated or pleated central portion and a plurality of circumferentially extending ribs on the outer surface of the sealing portions. This arrangement requires the sleeve to be formed by an extrusion process. Each expansion unit includes a channel-shaped band connected together by a threaded member. A nut on the threaded member, requiring the use of an open end wrench, is turned to spread the band apart. In addition to the inconvenience involved in turning the nut, the bands are vulnerable to being flexed by overtightening the nut, in which case the compressive force applied by the band is not uniform around the circumference of the sleeve.